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//! Definitions needed for computing data layout of types.
use std::cmp;
use la_arena::{Idx, RawIdx};
pub use rustc_abi::{
Abi, AbiAndPrefAlign, AddressSpace, Align, Endian, FieldsShape, Integer, IntegerType,
LayoutCalculator, Niche, Primitive, ReprFlags, ReprOptions, Scalar, Size, StructKind,
TargetDataLayout, TargetDataLayoutErrors, WrappingRange,
};
use crate::LocalEnumVariantId;
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct RustcEnumVariantIdx(pub LocalEnumVariantId);
impl rustc_index::vec::Idx for RustcEnumVariantIdx {
fn new(idx: usize) -> Self {
RustcEnumVariantIdx(Idx::from_raw(RawIdx::from(idx as u32)))
}
fn index(self) -> usize {
u32::from(self.0.into_raw()) as usize
}
}
pub type Layout = rustc_abi::LayoutS<RustcEnumVariantIdx>;
pub type TagEncoding = rustc_abi::TagEncoding<RustcEnumVariantIdx>;
pub type Variants = rustc_abi::Variants<RustcEnumVariantIdx>;
pub trait IntegerExt {
fn repr_discr(
dl: &TargetDataLayout,
repr: &ReprOptions,
min: i128,
max: i128,
) -> Result<(Integer, bool), LayoutError>;
}
impl IntegerExt for Integer {
/// Finds the appropriate Integer type and signedness for the given
/// signed discriminant range and `#[repr]` attribute.
/// N.B.: `u128` values above `i128::MAX` will be treated as signed, but
/// that shouldn't affect anything, other than maybe debuginfo.
fn repr_discr(
dl: &TargetDataLayout,
repr: &ReprOptions,
min: i128,
max: i128,
) -> Result<(Integer, bool), LayoutError> {
// Theoretically, negative values could be larger in unsigned representation
// than the unsigned representation of the signed minimum. However, if there
// are any negative values, the only valid unsigned representation is u128
// which can fit all i128 values, so the result remains unaffected.
let unsigned_fit = Integer::fit_unsigned(cmp::max(min as u128, max as u128));
let signed_fit = cmp::max(Integer::fit_signed(min), Integer::fit_signed(max));
if let Some(ity) = repr.int {
let discr = Integer::from_attr(dl, ity);
let fit = if ity.is_signed() { signed_fit } else { unsigned_fit };
if discr < fit {
return Err(LayoutError::UserError(
"Integer::repr_discr: `#[repr]` hint too small for \
discriminant range of enum "
.to_string(),
));
}
return Ok((discr, ity.is_signed()));
}
let at_least = if repr.c() {
// This is usually I32, however it can be different on some platforms,
// notably hexagon and arm-none/thumb-none
dl.c_enum_min_size
} else {
// repr(Rust) enums try to be as small as possible
Integer::I8
};
// If there are no negative values, we can use the unsigned fit.
Ok(if min >= 0 {
(cmp::max(unsigned_fit, at_least), false)
} else {
(cmp::max(signed_fit, at_least), true)
})
}
}
#[derive(Debug, PartialEq, Eq, Clone)]
pub enum LayoutError {
UserError(String),
SizeOverflow,
TargetLayoutNotAvailable,
HasPlaceholder,
NotImplemented,
Unknown,
}
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